Cave Knifefish

Eigenmannia vicentespelaea is a species of weakly electric knifefish in the family Sternopygidae. Native to the São Domingos karst area in central Brazil, it is the only known knifefish to exclusively inhabit caves. Measuring up to 12 cm (4.7 in) long, E. vicentespelaea can be distinguished from its relatives by its translucent body and reduced or absent eyes. As some individuals retain well-developed eyes, this fish may have colonized caves only recently in evolutionary time.